Sneak Preview

These letters. Such announcement. Many words.

In the next few days I will publish two – not one – but two articles on how to approach a problem on how to reverse engineer protocols. There have been to applications I looked into to code a library for my home uses.

#1 – MC3000 Charger

MC3000_Charger provides an USB and Bluetooth (BT) interface (Spoiler: I am not covering the BT interface. Not yet). The USB interface is used to update the firmware and to program and interact with the charger during charging.

The Windows software provided by SkyRC can program each slot individually to support different types of batteries with different charging capacities.

As a result of my analysis, and this will be one of the upcoming articles, I reversed the application and wrote a Python library. To do so I dissected a .NET application. So no big magic here!

#2 – LW12 WiFi LED Controller

This was a tricky one. It is a low budget Chinese WiFi LED controlled with a mobile app. The Android app I looked at was encrypted using a separate VM layer on-top of the Dalvik engine. (Spoiler: No need to reverse this, and I did not do it.)

Sometimes there are simpler solutions. This is what the second article will be about.

The controller itself comes by many names: Foxnovo and I remember buying it as a Lagute.

KTHXBYE.

Remote data acquisitions over ssh

To get your data trough ssh to your local storage, you simply use pipes. It does not matter if you use cat, dd or any other command line tool which outputs the data on standard output (stdout).

Using cat

When using cat the there is no need to add any additional parameters in your command chain. A simple cat <input> will suffice.

Cat does not have any progress information during read operations.

Using dd

The program dd requires more user interaction during the setup phase. To use dd you have to give the if= argument. The use of different blocksizes (bs) will not have that much of an impact on the speed. Feel free to have a look at this this.

´╗┐Wow. So scientific! Much CLI.

Examples

A simple example with no output to the terminal except of errors. The output to stderr is not suppressed.

 $ # Using cat to copy /dev/sda
 $ ssh <user@remotehost> 'cat /dev/sda' > sda.raw

If you want to suppress errors, use:

 $ # Using cat to copy /dev/sda
 $ ssh <user@remotehost> 'cat /dev/sda 2>/dev/null' > sda.raw

The next example will demonstrate the use of dd.

 $ # Using dd to copy /dev/sda
 $ ssh <user@remotehost> 'dd if=/dev/sda' > sda.raw

Of course you can suppress errors as well.

Speeding up the data acquisition and minor tweaks

With the basics covered, we can begin optimizing our data transfer. In the first step we speed up the transfer with gzip.

The argument -c will write the compressed data to stdout which will be piped to your local system.

Of course you can use this with cat as well.

 $ ssh <user@remotehost> 'dd if=/dev/sda | gzip -c' | gunzip > sda.raw

To add some progress information, you have two options with dd.

 $ # dd status
 $ ssh <user@remotehost> 'dd if=/dev/sda status=progress | gzip -c' \
 > | gunzip > sda.raw

The status argument writes the output to stderr and will not end up in your local copy.

 $ # dd through pv
 $ ssh <user@remotehost> 'dd if=/dev/sda | gzip -c' \
 > | pv | gunzip > sda.raw

Pv needs to be installed separatly. Check your packet manager. 0r teh Googlez!

KTHXBYE.

Update #01

Fixed a problem with in the examples. Had a pipe too much. #Fail